The monitoring of glucose levels is of vital importance in the clinical setting. In particular, the regular monitoring of tissue glucose concentrations by diabetic patients and the care of hypoglycemic patients in an intensive care environment require simple and reliable methods for monitoring glucose levels. Such glucose monitoring has usually been based on electrochemical technology and glucose selective enzymes such as glucose oxidase. Sensors based on this technology are susceptible to denaturing of the enzyme, particularly in a biological environment. Further, because they are consumptive of glucose and rely on constant diffusion of glucose to the sensor electrodes, they are susceptible to errors and drift.
An alternative technology to the electrochemical devices is the use of optical sensors, such as those based on fluorescence intensity measurements. For instance, reversible, non-consumptive fluorescent optical sensors utilizing fluorophore boronic acid chemistries as the indicator for glucose have been developed. Such sensors measure the change in the emitted fluorescent intensity as a means of determining glucose concentration. Such boronic acid glucose indicating chemistries have the advantage of being reversible with glucose, non-consumptive and are more stable than the enzymes, such as glucose oxidase, which are commonly used in electrochemical glucose sensors. They can also be readily immobilized, within a hydrogel, onto an optical fibre.
These sensors rely on the selective binding of glucose to the boronic acid binding site. Boronic acids, however, are capable of binding other saccharides, for example galactose and fructose. An effective sensor should therefore provide good selectivity for glucose over other saccharides.